1. Field of the Invention
This invention relates to an apparatus for measuring defects such as substrate fractures or internal cracks in relation to samples such as material substrates (photo-voltaic cell, polycrystalline silicon substrate).
2. Description of the Related Art
Conventionally, there is an apparatus disclosed in, for example, JP-A-7-113791 as a measuring apparatus for speedily objectively evaluating uniformity of samples without damaging samples such as material substrates.
FIG. 9 is a block diagram showing a uniformity measuring apparatus of the samples. This measuring apparatus comprises a vibrator 102 for applying vibration to the end of a flat plate sample 101, a first vibration sensor 103 which is spaced a predetermined distance away from the applied vibration portion of the vibrator 102 and detects the vibration transferring the sample 101, and a second vibration sensor 104 which is spaced a predetermined distance away from the vibration sensor 103 and detects the vibration transferring the sample 101.
The vibration applied by the vibrator 102 is transferred from the applied vibration portion of the sample 101 to the other end direction and is detected by the first and second vibration sensors 103 and 104. Vibration detection signals detected by the first and second vibration sensors 103 and 104, respectively, are fed to filters 105 and 106 for eliminating noise signals and selecting a signal with a predetermined frequency, and are amplified by amplifiers 107 and 108. The detection signal from the vibration sensor 103 is fed to a terminal of a channel 1 of an oscilloscope 109 and the detection signal from the second vibration sensor 104 is fed to a terminal of a channel 2 of the oscilloscope 109 and the detection signals are respectively displayed. Then, uniformity of the sample 101 can be evaluated by calculating a difference in vibration transfer time or a difference in transfer speed based on each of the detection signals displayed on the oscilloscope 109.
The conventional apparatus as described above employs a method for evaluating uniformity using the transfer time and the transfer speed of the vibration to the sample. That is, this determination method is a method for analyzing the difference in instantaneous data between two points (the difference in transfer time, the difference in transfer speed) rather than change with time to determine uniformity, fractures or cracks of the sample by calculation, so that enough results could not be obtained for detection of fractures and internal cracks of the point fixing the sample, detection of defects (fractures or internal cracks) of the distant point or the point equal from two points in a vibration transfer area inside the sample, and detection of fine microcracks.
The invention is implemented to solve such problems, and it is an object of the invention to be able to detect defects of a sample irrespective of size and place of the defects (fractures or internal cracks of a material substrate) of the sample while enabling objective evaluation without doing damage to the sample.
According to the invention, there is provided an apparatus for measuring defects of a sample, comprising an inspection jig including a sample mounting portion for mounting the sample, a vibrator for applying vibration to the sample and a sound collector for collecting a vibration sound when the vibration is applied to the sample by this vibrator, and a sound detector for conducting frequency analysis of the vibration sound collected by the sound collector, and the defects of the sample are determined by sampling and analyzing an applied vibration sound when the vibration is applied to the sample by the vibrator on the time series.
In the invention, the vibration sound collected by the sound collector is respectively amplified through a low-pass filter and a high-pass filter of the sound detector and then differential calculation is made and also, a composite wave is outputted to an oscilloscope.
In the invention, a fixing part for fixing the sample of the sample mounting portion is made of a cushioning material and the sample mounting portion is mounted on a shaft of an inspection jig fixation side through a bearing.
In the invention, the sample is resiliently pinched and fixed by the sound collector and the fixing part of the sample mounting portion.
According to a second aspect of the invention, there is provided a method for measuring defects of a sample, comprising the steps of applying vibration to the sample mounted in a sample mounting portion by a vibrator, collecting a vibration sound when the vibration is applied to the sample by this vibrator on the time series by a sound collector, and determining the defects of the sample by conducting frequency analysis of the vibration sound collected by the sound collector.
In the invention of claim 6, after the first determination of the defects of the sample is made, the sample rotated a predetermined angle is fixed and again, vibration is applied to the sample by the vibrator and the defects of the sample are determined.